After being expelled from Jordan in 1970, the Palestine Liberation Organization (PLO) set up a base of operations in Lebanon. Over the following years, this militant group converted Israel's hitherto peaceful border with Lebanon into a major confrontation point. Israel had initiated several limited actions against PLO bases in Lebanon in response.

By 1982, Lebanon was embroiled in a Civil War primarily between Christians and Muslims, with the PLO actively participating. Concurrently, the PLO intensified its attacks on Israel, prompting the Israeli Defense Minister, Ariel Sharon, to conclude that decisive action against the PLO in Lebanon was necessary.

On June 6, 1982, Israel launched a large-scale assault against the PLO in southern Lebanon. This attack instigated a brief yet decisive confrontation with Syria, resulting in Syria losing 81 aircraft and its entire anti-aircraft defense system.

Israeli troops chased the Palestinians all the way to Beirut, laying siege to the city for several months. Eventually, under the terms of a negotiated agreement, PLO leadership under Yasser Arafat agreed to go into exile in Tunis. In a subsequent turn of events, the leader of the Phalange, a Christian militia group, who had assumed the presidency, was assassinated. As retaliation, Phalange fighters entered a Palestinian refugee camp located in an area ostensibly controlled by Israel and killed 300 individuals.

In an attempt to maintain peace, a multinational force led by the United States entered Lebanon.